When components, in particular gas turbine components, are operated at high temperatures, their free surfaces are exposed to highly corrosive and/or oxidizing conditions. When employed in gas turbines, such components may be made for example of a super-alloy based on nickel. To protect them against corrosion and/or oxidation, such components are provided with coatings. To provide a corrosion-resistant and/or oxidation-resistant coating on a component, known methods already precipitate aluminum, and platinum if appropriate, on a substrate surface of the component, to provide a coating in the form of an aluminum substrate area or a platinum-aluminum substrate area. Compared to pure aluminum coatings, platinum-aluminum coatings have the advantage of increased resistance to oxidation and to corrosion from hot gases; such platinum-aluminum coatings are brittle, however, and thus have limited thermal-mechanical strength.
EP 0 784 104 B1 describes a component made of a nickel-based alloy with a platinum-aluminum substrate area, platinum first being precipitated onto a substrate surface of the component and then being diffused into the substrate surface to provide the platinum-aluminum substrate area. After that the component coated with platinum is alitized, in order to provide a platinum-aluminum substrate area that has an integrated aluminum content of 18% by weight to 20% by weight, an integrated platinum content of 18% by weight to 45% by weight, and the remainder components of the substrate composition.
The platinum-aluminum substrate area described in EP 0 784 104 B1, or the component described there having such a coating, has relatively low ductility, which results in limited thermal-mechanical strength (TMS), in particular limited HCF strength and LCF strength. Because of the limited thermal mechanical strength of the platinum-aluminum substrate area described there, cracks can form therein, limiting the durability of the coating.
It is also known from EP 0 784 104 B1 to apply a ceramic layer to the platinum-aluminum substrate area. However, the durability of the ceramic layer on the platinum-aluminum substrate area according to EP 0 784 104 B1 is limited.
Another component having a platinum-aluminum substrate area is known from U.S. Pat. No. 6,589,668 B1, the platinum-aluminum substrate area described there having an inner aluminum diffusion zone and an outer platinum-aluminum zone with a single-phase structure. The coating known from this related art also has limited thermal-mechanical strength, and thus limited durability.
U.S. Pat. No. 5,514,482 should also be referenced as related art, which describes a component onto whose substrate surface an aluminum substrate area of aluminum oxide is deposited, a ceramic layer being applied to this aluminum substrate area including an interposed thin aluminum film. This coating of a component also has limited thermal-mechanical strength, and thus limited durability.